The Queen has given the royal seal of approval to a new enclosure for endangered lions.
Accompanied by the Duke of Edinburgh, she opened the Zoological Society of London (ZSL)'s Land Of The Lions exhibit, which will be home to four endangered Asiatic lions.
Several murals of lions and monkeys decorated the old brick walls surrounding the enclosure, while a bright yellow cow with turquoise hooves and horns and floral decoration proudly guarded the entrance.
Guests were served mango bucks fizz with an edible flower and tea in keeping with the Indian theme as they waited for the royal couple.
A sign warned visitors not to cross the boundary fence due to "dangerous lions, dangerous ruins".
The Queen and Philip listened to speeches from ZSL president Sir John Beddington and director Ralph Armond, while lions prowled behind them in search of meat.
A stand-off between two of the lionesses over some lunch prompted the Queen to repeatedly glance behind her, as a loud roar interrupted the speeches.
She then unveiled a large plaque to commemorate the opening, while the Duke joked to staff: "Where are you putting that?"
Philip received a reproduction of a painting by Edward Lear circa 1835 of an Asian lion to accompany the publication The Maneless Lion Of Gujarat.
The Queen was presented with a photograph of her visit to the zoo 40 years ago, in 1976, when she opened the New Lion Terraces at almost the same spot.
Dame Vivien Duffield and her daughter Arabella were in that photograph and were also at Thursday's launch.
"You look a bit different", the Queen joked to Arabella, who was just four years old when the photo was taken, prompting laughter from the crowd.
The Queen wore a pale blue outfit and hat by Angela Kelly, which she last wore at the beacon lightings for VE Day in Windsor last May.